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(Fwd) Metal topic


#1

Forwarded Message FollowsFrom: James_Marker jmarker@gia.org
To: owner-orchid owner-orchid@proteus.imagiware.com
Subject: Metal topic
Date: Tue, 30 Jul 96 17:16:00 PDT

Reply to> I am told that after annealing silver often it is thrown into acid
to remove the firescale and fluxes whilst still hot. If this is done the
acid enters the pores of the metal and when the metal cools the acid is
trapped inside the metal. To prevent this only place cold items in acid.

Reply to> If one has an item that has been annealed hot or is causing an
allergic reaction one should re-heat the item and anneal it in a dilute
bi-carb or washing soda solution

James Marker in the Library at GIA here. I sent the above series of message
to a few metalworkers I know for comment & what follows here is the combined
set of comments from them. One recommended a book called - “An Introduction
to Precious Metals” by Mark Grimwade. It is an out-of-print book, but, if
obtainable, (they said) worth looking at. I hope their comments help the
discussion.

Reply to> …told that after annealing silver…

Annealing silver is done to reorder the CRYSTALLINE structure of the metal,
to allow the compacted crystals (as the result of work hardening) to reform
into stress relieved crystals. This allows work to continue on the metal
without the metal going beyond its crystal grain boundary and shear. This
results in the metal breaking. This breaking may be erroneously interpreted
as a “pore”.

Reply to> If this is done acid enters the “pores”…

Perhaps this person is confusing “porosity” with metal having pores.
Porosity occurs when the molten metal absorbs gasses in its liquid state.
This is generally observed as minute pinholes in a finished piece of jewelry
at 10X . When metal is in the pickle solution it should be removed and
dipped into a saturated solution of baking soda and water which will
neutralize any remaining acid on the metal, then rinsed in clean water.

Reply to> …to prevent this…

This statement shows a fundamental misunderstanding of crystal growth. While
I agree that the item is best quenched in a cold liquid, the jeweler whom
practices safely will use water as the quenching medium for two reasons.
One- placing hot metal in hot pickle creates more deadly fumes for the
jeweler to inhale; not good. Two- Hot metal in hot pickle can splash onto
the jeweler (eyes, clothes, and skin etc.) which just indicates several
safety issues that should be addressed.

After quenching in cool water to insure the crystal growth is “frozen”, then
the metal is placed into pickle to remove any oxides which may have formed
during the annealing process. (FYI- there are various substances pickle can
be made out of.)

Reply to> …if one has an item which as been annealed hot…

All items are annealed hot.

Allergic reactions are generally caused by two things. 1) Human metabolic
rejection of the alloying metal in the jewelry (i.e.; copper in sterling).
2) Rare interaction between the alloying metals and outside stuff like hand
cream, body lotion, perfume, detergents etc. So annealing in a solution of
bi-carb or soda is doesn’t make sense.


#2

Dr. E. Aspler wrote:

Forwarded Message Follows
From: James_Marker jmarker@gia.org
To: owner-orchid owner-orchid@proteus.imagiware.com
Subject: Metal topic
Date: Tue, 30 Jul 96 17:16:00 PDT

Reply to> I am told that after annealing silver often it is thrown into acid

James Marker in the Library at GIA here. I sent the above series of message
to a few metalworkers I know for comment & what follows here is the combined
set of comments from them. One recommended a book called - “An Introduction
to Precious Metals” by Mark Grimwade.

Hey Jim,

Thanks for the reasearch! Those staments made little sence, but I
coudn’t document as well as you.

Thanks agian,
JoeB